School holidays are the perfect time for schools to develop their sites – especially on floors, when the kids and the teachers are off relaxing or studying and contractors have days or weeks to get in, remove the old and replace with new.

Somersham Primary School in Huntingdon decided to do just that, schedule works for Spring half term and install underfloor heating and a new screed and covering in two brand new classrooms.

The contractors levelled the concrete floor slab, laid a damp proof membrane and 75mm of insulation. Hot water underfloor heating pipes were then installed followed by a 75mm thick Ronascreed 8 Day Overlay floating floor screed to protect the insulation and bring to final floor level prior to fitting carpet.

The new building will be opened for use by the school at the beginning of the 2011/12 academic year. In order to ensure all works were completed in time the screed specification needed to be upgraded to dry out faster; so specifiers Capita Architecture included Ronascreed 8 Day Overlay, a liquid admixture manufactured by Ronacrete, in the site batched screed. A conventional 75mm sand and cement screed will typically dry out at the rate of 0.5mm per day in good drying conditions – a total of 150 days or 21 weeks – too long for this project. The addition of Ronascreed 8 Day Overlay would ensure the screed was suitably dry after approximately three weeks.

Ronascreed 8 Day Overlay admixture is easily and simply added to the screed as it is mixed; the screed is then laid using conventional screeding techniques. To monitor how quickly the screed is drying, the relative humidity (RH) is measured using a hygrometer. Once it has fallen to below 75% it is dry enough to receive vinyl or carpet. In good drying conditions, a 50mm Ronascreed 8 Day Overlay screed will be dry enough to receive moisture sensitive coverings after only 8 days without the need for a surface applied DPM.

Main contractors Ashe Construction appointed Unican Construction to install the 75mm floating screed. Two teams of screeders mixed and pumped the modified screed mix into the classrooms using a Putzmeister screed pump. 330m² of screeding was completed in one day and the screed was left to dry, measuring the RH as each day passed.

Ronascreed 8 Day Overlay has been used on many small and prestige projects including the Barbican Centre, Heathrow Airport, London Stock Exchange and Wembley Stadium.